Field of the Invention
The present invention relates to a laundry treatment apparatus for reducing an eccentric amount of a drum and, more particularly, to a laundry treatment apparatus including a balancer capable of active control.
Discussion of the Related Art
A conventional laundry treatment apparatus includes a cabinet forming an external appearance, a tub included within the cabinet and for storing water, a drum rotatably provided within the tub for storing laundry, and a driving unit to rotate the drum.
The drum may be rotated without maintaining a dynamic equilibrium depending on laundry stored therein.
The dynamic equilibrium means “the state in which total moment generated by a centrifugal force or a centrifugal force becomes 0 with respect to the rotation axis when a rotating body is rotated”. In the case of a rigid body, an ideal dynamic equilibrium is maintained if a mass distribution is constant around the rotation axis.
Such an ideal dynamic equilibrium, although it is practically impossible, may be considered to be an actual dynamic equilibrium state if a mass distribution of laundry is in a permissible range (if a drum is rotated while being vibrated within the permissible range) around the rotation axis of the drum when the drum is rotated in the state in which the laundry has been stored in the laundry treatment apparatus.
In contrast, the state in which an actual dynamic equilibrium has been broken (i.e., unbalance) in the laundry treatment apparatus is generated when the degree to which a mass distribution has become eccentric based on the rotation axis of the drum when the drum is rotated exceeds a permissible range.
The drum rotated in the unbalance state is vibrated along with rotation, and the vibration of the drum is delivered to the tub or the cabinet, causing noise.
In order to reduce such eccentricity of the drum, a conventional laundry treatment apparatus includes a ball balancer or fluid balancer having a ball or a fluid received in a housing fixed to the drum. In particular, a front loading type laundry treatment apparatus inclined toward the front, that is, the rotation axis of the drum has the fastest speed when laundry causing the eccentricity of the drum in the unbalance state passes through the lowest point of a drum rotation track and has the slowest speed when the laundry causing the eccentricity of the drum in the unbalance state passes through the highest point of the drum rotation track. Accordingly, the ball balancer or the fluid balancer included in the conventional laundry treatment apparatus functions to reduce eccentricity in such a manner that the ball or the fluid moves toward the lowest point of the drum rotation track when the laundry causing eccentricity moves toward the highest point.